Laurence (in any spelling) is an extremely unusual name on the Island - found only three times pre 1750 associated with a Manx family name (in wills + burials) no baptism + never in association with Kelly name;
If he returned for a legacy then there will be a will - kelly is most common family name on Island (it was also a common Irish name and many Kellys are indicated as Irish in 18th C) - assuming it was between 1740 and 1770 then there are some 350 kelly,kelley or killey wills - on manxnotebook (tab line above) you will find summaries of about 50% of these - no laurance - allowing a typical 20 mins to find a specific will, you have some 50 hours of work to find the needle in the haystack if indeed it exists